1. Field of the Invention
The present invention relates to an electric current distribution system for automotive vehicles which distributes an electric current from an alternator or a battery to the respective loads by way of fuses and relays of series circuits in a junction box.
2. Description of the Prior Art
The prior art electric current distribution systems for automotive vehicles are, for example, constructed as shown in FIG. 3. Specifically, one end of a fusible link 4 is connected with a positive terminal of a battery 3 whose negative terminal is grounded and one end of another fusible link 2 is connected with an alternator (ALT) 1. The other ends of the fusible links 2 and 4 are both connected with an input terminal of a junction box 5 installed in an engine compartment. Ends of loads 7 such as lamps, motors and ignition systems are connected with a plurality of output terminals of the junction box 5 directly or by way of a switch 6, and the other ends thereof are grounded.
The junction box 5 accommodates a plurality of series circuits between its input and output terminals. The series circuits consist essentially of fuses FS and relays RL. For example, when the switch 6 is turned on, the respective relay RL acts to supply an electric current to the respective load 7.
During the starting of an engine after an ignition switch is turned on, an electric current from the battery 3 is supplied to the junction box 5. After the starting of the engine, an electric current obtained by rectifying an alternating current generated in the alternator 1 is supplied to the battery 3, to the junction box 5, and consequently to the respective loads 7.
Since the alternator 1 stops generating power in the event of a car crash, no electric current is supplied to the junction box 5 from the alternator 1, but an electric current from the battery 3 is still supplied to the junction box 5. Thus, even if the car crash results in a burnout or short circuit, the circuits cannot immediately be disconnected in the above construction. As a result, a variety of problems may arise due to an overcurrent.
In order to enable an emergency stop of power supply from a battery to electric parts (loads) in the event of the car crash, the construction as disclosed in Japanese Unexamined Patent Publication No. 58-164457 was proposed. An emergency cutoff mechanism including a relay, a relay drive transistor for opening and closing the relay and a control circuit for controlling the relay drive transistor is provided between each load and the battery of the automotive vehicle. There is also provided an impact detection mechanism for, upon detecting a deceleration of a specified level or higher, sending to the control circuit a signal used to control the relay drive transistor so as to cut off the power supply.
However, the construction disclosed in the above publication is complicated because the emergency cutoff mechanism needs to include the control circuit for controlling the relay drive transistor.
In view of the above problem, it is an object of the invention to provide a simple construction for enabling a secure cutoff of an electric current supply to loads in the event of a car crash.
In this invention, in the event of a car crash, the earthing means acts in response to the output from the crash sensor (e.g., air bag sensor) to bypass an electric current flowing into the input terminal of the junction box by way of the fusible link to the earth. Thereby, the fusible link is heated and fused, cutting off the flow of electric current to the respective loads. Particularly, the earthing means may comprise a relay or a transistor.
Since the earthing means may simply be constructed with a relay or a transistor, the flow of electric current to the loads in the event of the car crash can be cut off by this simple construction.